An object in motion tends to stay in motion at a constant speed, in a constant direction, unless compelled to change by another force impressed upon it.
History
Before Sir Isaac Newton presented his Laws of Motion, Galileo formulated the concepts of inertia and acceleration due to gravity. Before Galileo, Aristotle distinguished between natural motion and violent motion. The concept of violent motion led to the concept of force, which is one of the most significant parts of physics. Motion begins, ends, and changes according to the force or forces applied to an object. Galileo further expanded on the concept of force when he developed the concept of friction by comparing the results of balls rolled on smooth and rough surfaces. Newton further researched these ideas and theories and then in 1686 presented his Three Laws of Motion in the "Principia Mathematica Philosophiae Naturalis." Newton stated that when an object is at rest it will remain at rest until a force acts upon it sending it in motion. He also concluded that the objects would continue moving forever without a force, such as friction, to slow and stop them. Using this knowledge, Newton formed his first law, often known as "Newton's Law of Inertia." The second law and third law deal with acceleration and interactions. But what makes the first law so special is that it was developed by the accumulation of research and knowledge of multiple generations of scientists. It is extremely important because it is the foundation for Laws two and three. [2] [5] [8] [10] [16]
Force
Force is a crucial concept in Newton's First Law Of Motion. In order for any object to be set in motion, it must be influenced by an unbalanced force. The same is true in order for an object to cease its motion. Without force, moving objects would continue on forever and resting objects would remain motionless. The most common force is friction. Every moving object creates friction whether they interact with a rigid surface such as concrete, or something as small and unnoticeable as air molecules. Galileo was the first person to discover friction by rolling balls along different surfaces. The smoother the surface, the weaker the force of friction. The ball, therefore, rolled further than it did across a rough surface, which created a larger amount of frictional force. Although two objects may appear to be smooth to the naked eye, a microscopic view would show that they are actually covered with tiny bumps and resistant to movement. There are definitely some negative aspects to friction, but it is essential to life. Walking would be impossible without the presence of friction. In many real world situations, friction opposes motion, so a constant force is required for an object to remain in continuous motion.
Courtesy of Ron Kurtus' School for Champions
If friction is a force that affects every moving object, how is movement possible? The answer is something called "net force." Since every object requires an applied force to be put in motion, and every moving object interacts with some sort of friction, there is always more than one force applied to any traveling object. If there are two forces acting on the same object, then the net force is the combination of these two forces. The SI unit of force is the newton, named after the same scientist that developed the three laws of motion. In order for the object to be set in motion, either both forces would have to be compelling the object to move in the same direction, or one force would have to overpower the other. For example, if two different forces are applied to an object, the first of which is pulling with a strength of ten newtons to the right and the second pushing with a strength of five newtons, also to the right, the net force would be fifteen newtons (assuming friction is negligible), causing the object to move to the right; however, if the first force remains pulling the object with a strength of ten newtons to the right, but the second force pulls, this time to the left, with a strength of five newtons, the object will still be compelled to move to the right, but the net force will only be five newtons. If both objects pull in opposite directions with the same amount of force, the net force is zero and the object is at rest. [1] [3] [6] [9] [11] [12] [17]
Equilibrium
When an object is at rest or moving at a constant velocity (moving without acceleration), it is said to be in a state of equilibrium. This means that all the forces applied to the object are being cancelled out
Image Courtesy of University of Redlands
by one another. Not only are the horizontal forces balanced, but the vertical ones are as well. The force of gravity plays a major role in the concept of equilibrium. For instance the force of gravity is pulling an object downward, and that object is resting on an elevated surface, such as a table, then the table must push up on the object with the same amount of force. This force is called a support force and is often known as the normal force. Since the atoms in the object are pushing down on the atoms in the tabletop, the atoms in the table have to push back with an equal amount of force in order to maintain its state of equilibrium. If gravity pulls down on a hanging object, then whatever it is hanging from must be pulling up with an equal amount of force. The supporting object will either snap or break if it is unable to exert a force greater than or equal to the downward force on the object in equiibrium. Although it does not appear so, the table pushes up with the same amount of force as the object sitting on it pushes down. In addition to the vertically implied forces, the same concept exist for horizontal forces. For example, if a ladder is leaning on a wall then the wall pushes back with the same amount of force as the ladder in order to support its weight. In this case the step in the ladder would also be matching the force of whoever was standing on it by exerting an upward force. Equilibrium is often taken for granted. Balance is a form of equilibrium. Balance is the ability of an object to support its center of mass. The center of mass is the point around which all mass of a system is balanced. When the center of mass of a system is beyond the supports, the equilibrium is offset and the system falls. People do not usually worry when they are about to sit in a chair or lean up against a bookshelf. But if either of these objects are unable to exert the same force as the individual resting on them, that person is going to be in a world of hurt… physically.
Mass
Mass is a measure of an object's inertia, or resistance to forces. It is determined by the amount of matter in an object and is measured in kilograms. One kilogram equals approximately 9.8 newtons. Mass is often confused with weight, but the two terms mean different things. Weight varies depending on location and is measured by the gravitational pull on an object. For instance, an object on Earth would weigh more than the same object would weigh on the moon because the gravitational pull on Earth is much stronger. Mass measures the amount of matter in an object and is constant, which means it is the same no matter where it is measured. The amount and types of atoms in an object determines its mass. The larger an object's mass, the more inertia it has, which makes setting it into motion more difficult. Mass does not necessarily mean size, though. Although an object may appear to be larger than another, its mass may not be as great as a denser, more compact object. For example, a basketball is slightly larger than a bowling ball, but a bowling ball is denser, and thus contains more mass. More force is required to move an object with a large mass than to move an object with a small mass. In order for an object to begin its motion, a force stronger than its mass is needed, and the same is true to stop an object. Objects with large mass require large amounts of force to bring them to a stop. The force of friction always acts against an object's motion, but any outside force, including another moving object, can halt a moving object. [1] [4] [6] [7] [9] [15] [17]
Vectors
Picture Courtesy of The Physics Department
Vectors are values that include both magnitude and direction. The figure to the right shows both the X and Y components of the vector. This illustrates how objects moving along a diagonal path have motion in both the X and Y directions. When two or more forces act on an object, each compelling it to move in a different direction, the object moves along a vector. The X component of the vector runs horizontally and determines how far to the left or right that an object will move. The Y component is vertical and determines how high the object will go. Combined, the two components form an angle, or vector. Simply put, a vector is the addition of the forces applied to an object compelling it to move. If one force is compelling the object to move at an angle of fifty degrees, and another separate force is compelling the object to move at an angle of forty degrees, the addition of the forces would result in a vector, and the object would move at an angle of forty five degrees. Each component of a vector is independent. A freefalling object travels downward with the same speed as an object that is moving both down and sideways at the same time. Since each component is independent of the other, the downward motion of both objects is the same, even though one affected by two forces is falling in a parabolic shape. An object can move horizontally and then vertically in two different motions, or it can just move once in a diagonal vector with the same magnitude and vector and end up in the same position.
Another type of vector determines the tension on ropes and wires supporting a weight of any kind. The wider the angle of the ropes supporting the weight, the more force is required to maintain the balance and equilibrium. If to much force is required to maintain this balance, then the tension builds up and the rope will snap. One example is a clothesline. If hung vertically it is very strong but if stretched out horizontally, it is unable to hold as much weight and will bow in the middle. If too much weight is added, it will snap.
[1] [6] [9] [13] [17]
Vocabulary
Force- An influence applied to an object that changes its state of motion. Friction - The force between touching materials as they move past each other. Inertia- An object's resistance to forces and change of motion. Mass- Always measured in kilograms, it is the quantity of matter in an object. It is the measure of inertia. Natural Motion - Thought to be straight up or straight down. The theory was that objects seek their natural resting places, Net Force - The resulting force when two or more forces are applied to the same object Newton - The SI unit of force, represented by the symbol "N" Vector - The addition of the forces on an object, resulting in both magnitude and direction. Violent Motion - Motion resulting from the application of forces on an object Weight - the force of gravity on an object
Newton's First Law of Motion
An object in motion tends to stay in motion at a constant speed, in a constant direction, unless compelled to change by another force impressed upon it.
History
Before Sir Isaac Newton presented his Laws of Motion, Galileo formulated the concepts of inertia and acceleration due to gravity. Before Galileo, Aristotle distinguished between natural motion and violent motion. The concept of violent motion led to the concept of force, which is one of the most significant parts of physics. Motion begins, ends, and changes according to the force or forces applied to an object. Galileo further expanded on the concept of force when he developed the concept of friction by comparing the results of balls rolled on smooth and rough surfaces. Newton further researched these ideas and theories and then in 1686 presented his Three Laws of Motion in the "Principia Mathematica Philosophiae Naturalis." Newton stated that when an object is at rest it will remain at rest until a force acts upon it sending it in motion. He also concluded that the objects would continue moving forever without a force, such as friction, to slow and stop them. Using this knowledge, Newton formed his first law, often known as "Newton's Law of Inertia." The second law and third law deal with acceleration and interactions. But what makes the first law so special is that it was developed by the accumulation of research and knowledge of multiple generations of scientists. It is extremely important because it is the foundation for Laws two and three. [2] [5] [8] [10] [16]
Force
Force is a crucial concept in Newton's First Law Of Motion. In order for any object to be set in motion, it must be influenced by an unbalanced force. The same is true in order for an object to cease its motion. Without force, moving objects would continue on forever and resting objects would remain motionless. The most common force is friction. Every moving object creates friction whether they interact with a rigid surface such as concrete, or something as small and unnoticeable as air molecules. Galileo was the first person to discover friction by rolling balls along different surfaces. The smoother the surface, the weaker the force of friction. The ball, therefore, rolled further than it did across a rough surface, which created a larger amount of frictional force. Although two objects may appear to be smooth to the naked eye, a microscopic view would show that they are actually covered with tiny bumps and resistant to movement. There are definitely some negative aspects to friction, but it is essential to life. Walking would be impossible without the presence of friction. In many real world situations, friction opposes motion, so a constant force is required for an object to remain in continuous motion.
If friction is a force that affects every moving object, how is movement possible? The answer is something called "net force." Since every object requires an applied force to be put in motion, and every moving object interacts with some sort of friction, there is always more than one force applied to any traveling object. If there are two forces acting on the same object, then the net force is the combination of these two forces. The SI unit of force is the newton, named after the same scientist that developed the three laws of motion. In order for the object to be set in motion, either both forces would have to be compelling the object to move in the same direction, or one force would have to overpower the other. For example, if two different forces are applied to an object, the first of which is pulling with a strength of ten newtons to the right and the second pushing with a strength of five newtons, also to the right, the net force would be fifteen newtons (assuming friction is negligible), causing the object to move to the right; however, if the first force remains pulling the object with a strength of ten newtons to the right, but the second force pulls, this time to the left, with a strength of five newtons, the object will still be compelled to move to the right, but the net force will only be five newtons. If both objects pull in opposite directions with the same amount of force, the net force is zero and the object is at rest. [1] [3] [6] [9] [11] [12] [17]
Equilibrium
When an object is at rest or moving at a constant velocity (moving without acceleration), it is said to be in a state of equilibrium. This means that all the forces applied to the object are being cancelled out
Mass
Mass is a measure of an object's inertia, or resistance to forces. It is determined by the amount of matter in an object and is measured in kilograms. One kilogram equals approximately 9.8 newtons. Mass is often confused with weight, but the two terms mean different things. Weight varies depending on location and is measured by the gravitational pull on an object. For instance, an object on Earth would weigh more than the same object would weigh on the moon because the gravitational pull on Earth is much stronger. Mass measures the amount of matter in an object and is constant, which means it is the same no matter where it is measured. The amount and types of atoms in an object determines its mass. The larger an object's mass, the more inertia it has, which makes setting it into motion more difficult. Mass does not necessarily mean size, though. Although an object may appear to be larger than another, its mass may not be as great as a denser, more compact object. For example, a basketball is slightly larger than a bowling ball, but a bowling ball is denser, and thus contains more mass. More force is required to move an object with a large mass than to move an object with a small mass. In order for an object to begin its motion, a force stronger than its mass is needed, and the same is true to stop an object. Objects with large mass require large amounts of force to bring them to a stop. The force of friction always acts against an object's motion, but any outside force, including another moving object, can halt a moving object. [1] [4] [6] [7] [9] [15] [17]
Vectors
Vectors are values that include both magnitude and direction. The figure to the right shows both the X and Y components of the vector. This illustrates how objects moving along a diagonal path have motion in both the X and Y directions. When two or more forces act on an object, each compelling it to move in a different direction, the object moves along a vector. The X component of the vector runs horizontally and determines how far to the left or right that an object will move. The Y component is vertical and determines how high the object will go. Combined, the two components form an angle, or vector. Simply put, a vector is the addition of the forces applied to an object compelling it to move. If one force is compelling the object to move at an angle of fifty degrees, and another separate force is compelling the object to move at an angle of forty degrees, the addition of the forces would result in a vector, and the object would move at an angle of forty five degrees. Each component of a vector is independent. A freefalling object travels downward with the same speed as an object that is moving both down and sideways at the same time. Since each component is independent of the other, the downward motion of both objects is the same, even though one affected by two forces is falling in a parabolic shape. An object can move horizontally and then vertically in two different motions, or it can just move once in a diagonal vector with the same magnitude and vector and end up in the same position.
Another type of vector determines the tension on ropes and wires supporting a weight of any kind. The wider the angle of the ropes supporting the weight, the more force is required to maintain the balance and equilibrium. If to much force is required to maintain this balance, then the tension builds up and the rope will snap. One example is a clothesline. If hung vertically it is very strong but if stretched out horizontally, it is unable to hold as much weight and will bow in the middle. If too much weight is added, it will snap.
[1] [6] [9] [13] [17]
Vocabulary
Force- An influence applied to an object that changes its state of motion.
Friction - The force between touching materials as they move past each other.
Inertia- An object's resistance to forces and change of motion.
Mass- Always measured in kilograms, it is the quantity of matter in an object. It is the measure of inertia.
Natural Motion - Thought to be straight up or straight down. The theory was that objects seek their natural resting places,
Net Force - The resulting force when two or more forces are applied to the same object
Newton - The SI unit of force, represented by the symbol "N"
Vector - The addition of the forces on an object, resulting in both magnitude and direction.
Violent Motion - Motion resulting from the application of forces on an object
Weight - the force of gravity on an object
References
1 Astronomy 161 - 1st law of motion
2. Encyclopedia Britannica- Isaac Newton
3. Fear of Physics- friction
4. Hyperphysics- mass and weight
5. Isaac Newton Institute for Mathematical Sciences- Issac Newton
6. Kim Rustow at Wisc-Online- 1st law
7. Math and Science Activity Center - mass and weight
8. Mathpages- natural and violent motions
9. National Aeronautics and Space Administration- 1st law
10. Paul A. Heckert, Newton's Laws for Kids- Newton
11. Practical Physics- forces and motion
12. Ron Kurtus' School for Champions- friction
13. The Physics Department - vectors
14. TheScienceClassroom Wikispace- Galileo Galilei
15. University of Colorado Guide to Physics- mass and weight
16. Washington Universtity in St. Louis- Isaac Newton
17. Zona Land- 1st law